Gene Summary

Gene:ATG5; autophagy related 5
Aliases: ASP, APG5, APG5L, hAPG5, APG5-LIKE
Summary:The protein encoded by this gene, in combination with autophagy protein 12, functions as an E1-like activating enzyme in a ubiquitin-like conjugating system. The encoded protein is involved in several cellular processes, including autophagic vesicle formation, mitochondrial quality control after oxidative damage, negative regulation of the innate antiviral immune response, lymphocyte development and proliferation, MHC II antigen presentation, adipocyte differentiation, and apoptosis. Several transcript variants encoding different protein isoforms have been found for this gene. [provided by RefSeq, Sep 2015]
Databases:VEGA, OMIM, HGNC, Ensembl, GeneCard, Gene
Protein:autophagy protein 5
Source:NCBIAccessed: 16 March, 2017


What does this gene/protein do?
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Pathways:What pathways are this gene/protein implicaed in?
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Cancer Overview

Research Indicators

Publications Per Year (1992-2017)
Graph generated 16 March 2017 using data from PubMed using criteria.

Literature Analysis

Mouse over the terms for more detail; many indicate links which you can click for dedicated pages about the topic.

Tag cloud generated 16 March, 2017 using data from PubMed, MeSH and CancerIndex

Specific Cancers (6)

Data table showing topics related to specific cancers and associated disorders. Scope includes mutations and abnormal protein expression.

Note: list is not exhaustive. Number of papers are based on searches of PubMed (click on topic title for arbitrary criteria used).

Latest Publications: ATG5 (cancer-related)

Zhang Q, Wu S, Zhu J, et al.
Down-regulation of ASIC1 suppressed gastric cancer via inhibiting autophagy.
Gene. 2017; 608:79-85 [PubMed] Related Publications
As autophagy has anti-apoptosis effect and accelerates cell survival, many studies start to target autophagy as a therapeutic strategy for cancer. Acid-sensing ion channels (ASICs) was reported to activate autophagy. However, whether ASICs can regulate gastric cancer through autophagy is unknown. The differentially expressed genes in normal gastric tissue and gastric cancer tissue in patients were investigated by RNA-seq. Expression of ASIC1 and autophagy related 5 (ATG5) was further confirmed by real-time PCR. Effects of knockdown expression of ASIC1 and ATG5 on the growth of gastric SGC-7901 cells were assayed by CCK-8 kit. The animal survival rate and tumor volume in murine heterotopic xenograft model was assayed. The expression of autophagy related genes was enriched in gastric cancer tissue in patients, including ASIC1 and ATG5. Knockdown expression of ASIC1 and ATG5 inhibits the growth of SGC-7901 cells, respectively. ASIC1 regulates ATG5 gene expression in SGC-7901 cells. ASIC1 knockdown extended the survival rate of animals and inhibited the tumor volume in the murine heterotopic xenograft model. This study showed that downregulation of ASIC1 inhibits gastric cancer growth via decreasing autophagy, therefore strongly suggests a therapeutic role for ASIC1 in gastric cancer.

Zheng X, Chen W, Hou H, et al.
Ginsenoside 20(S)-Rg3 induced autophagy to inhibit migration and invasion of ovarian cancer.
Biomed Pharmacother. 2017; 85:620-626 [PubMed] Related Publications
BACKGROUND: Autophagy maintains cellular homeostasis through engulfing cytoplasmic proteins and organelles, and plays an important role in cancer initiation and progression. Ginsenoside 20(S)-Rg3, an active ingredient of Panax ginseng, exerts anti-cancer functions in various cancers. However, its molecular mechanisms, including its effect on autophagy, are not fully elucidated in tumor models.
METHODS: Ovarian cancer cell line SKOV3 was treated by various concentrations of 20(S)-Rg3. Markers of autophagy were detected by real-time PCR, western blot, immunofluorescence and immunohistochemistry. Cell viability was observed by CCK8 assays and cell migration and invasion were examined with Transwell.
RESULTS: 20(S)-Rg3 induced autophagy in SKOV3 ovarian cancer cells in a dose-dependent manner as indicated by the upregulation of autophagy-associated molecules including LC3 II, ATG5 and ATG7. The autophagy inhibitor chloroquine antagonized the inhibition of 20(S)-Rg3 on migration and invasion of SKOV3 cells, but slightly enhanced the impairment of 20(S)-Rg3 on cell viability. Immunohistochemistry staining of LC3, ATG5 and ATG7 on subcutaneous xenograft tissue sections from previously established nude mice models showed that 20(S)-Rg3 upregulated LC3, ATG5 and ATG7 as observed in cell models.
CONCLUSION: Autophagy induction was one mechanism mediating inhibition of 20(S)-Rg3 on ovarian cancer invasive progression.

Ji GH, Cui Y, Yu H, Cui XB
Profiling analysis of FOX gene family members identified FOXE1 as potential regulator of NSCLC development.
Cell Mol Biol (Noisy-le-grand). 2016; 62(11):57-62 [PubMed] Related Publications
Lung cancer is one of the most malignant tumors worldwide with a high mortality rate, which has not been improved since several decades ago. FOX gene family members have been reported to play extensive roles in regulating many biological processes and disorders. In order to clarify the contribution of FOX gene family members in lung cancer biology, we performed expression profiling analysis of FOX gene family members from FOXA to FOXR in lung cancer cell lines and tissue specimens by Real-time PCR, western blot and immunohistochemistry analysis. We found that FOXE1 was the only gene which was over-expressed in six out of eight lung cancer cell lines and human cancer tissue specimens (28 out of 35 cases with higher expression and 7 out of 35 cases with moderate expression). Further investigation showed that MMP2 gene was up-regulated, and autophagy markers such as LC3B, ATG5, ATG12 and BECLIN1, were down-regulated concomitant with the increase of FOXE1. These results implicated that FOXE1 may be an important regulator by targeting autophagy and MMPs pathways in lung cancer development.

Graboń W, Otto-Ślusarczyk D, Chrzanowska A, et al.
Lactate Formation in Primary and Metastatic Colon Cancer Cells at Hypoxia and Normoxia.
Cell Biochem Funct. 2016; 34(7):483-490 [PubMed] Related Publications
High glucose consumption and lactate synthesis in aerobic glycolysis are a hallmark of cancer cells. They can form lactate also in glutaminolysis, but it is not clear how oxygen availability affects this process. We studied lactate synthesis at various oxygen levels in human primary (SW480) and metastatic (SW620) colon cancer cells cultured with L-Ser and/or L-Asp. Glucose and lactate levels were determined colorimetrically, amino acids by HPLC, expression of AST1-mRNA and AST2-mRNA by RT-PCR. In both lines glucose consumption and lactate synthesis were higher at 10% than at 1% oxygen, and lactate/glucose ratio was increased above 2.0 by L-Asp. AST1-mRNA expression was independent on oxygen and cell line, but AST2-mRNA was lower at hypoxia in SW480. We conclude that, in both cell lines at 1% hypoxia, lactate is formed mainly from glucose but at 10% normoxia also from L-Asp. At 10% normoxia, lactate synthesis is more pronounced in primary than metastatic colon cancer cells.

Morabito F, Voso MT, Hohaus S, et al.
Panobinostat for the treatment of acute myelogenous leukemia.
Expert Opin Investig Drugs. 2016; 25(9):1117-31 [PubMed] Related Publications
INTRODUCTION: Therapeutic strategies in patients with acute myeloid leukemia (AML) have not changed significantly over the last decades. Appropriate strategies are ultimately driven by the assessment of patients' fitness to define suitability for intensive induction chemotherapy, which produces high initial remission rates but, increased likelihood of relapse. Old/unfit AML patients still represent an urgent and unmet therapeutic need. Epigenetic deregulation represents a strategic characteristic of AML pathophysiology whereby aberrant gene transcription provides an advantage to leukemic cell survival. Efforts to re-establish impaired epigenetic regulation include hypomethylating agents and histone deacetylase inhibitors (HDACi).
AREAS COVERED: The review discusses the underlying mechanisms leading to disruption of lysine acetyltransferases (KAT or HAT)/deacetylase (KDAC or HDAC) balance and the rationale for using the HDACi panobinostat (LBH-589) in AML.
EXPERT OPINION: Although panobinostat has produced significant results in myeloma, its efficacy remains limited in AML. Panobinostat exerts pleiotropic activity and lack of specificity, which likely contributes to its inadequate safety in elderly AML patients. Phase I-II trials, utilizing panobinostat associated with well-known chemotherapeutic agents are ongoing and combinations with other druggable targets may likely be evaluated in future trials. The clinical use of this HDACi in AML the near future does not appearing promising.

Capett MS, Vollú-Silva P, Melchiades VA, et al.
Characterization of Ciprofloxacin-Resistant and Ciprofloxacin-Susceptible Uropathogenic Escherichia coli Obtained from Patients with Gynecological Cancer.
Curr Microbiol. 2016; 73(5):624-32 [PubMed] Related Publications
The objective of this work was to assess the genetic characteristics of uropathogenic Escherichia coli, ciprofloxacin resistance or susceptibility, obtained from patients with gynecological cancer and urinary tract infection (UTI). Seventy-seven E. coli ciprofloxacin-resistant isolates and 38 ciprofloxacin-susceptible were analyzed by polymerase chain reaction (PCR) to determine the phylogenetic groups, virulence factors as iucC, fyuA, hlyC, cnf1 genes, and pks pathogenicity island. The presence of genes related to ciprofloxacin resistance such as qnrA, qnrB, qnrS, aac(6')-Ib-cr, and qepA, and the sequencing of DNA gyrase genes and topoisomerase IV were determined. The genetic profile of the isolates was determined by pulsed-field gel electrophoresis (PFGE). Statistical analysis was performed using Fisher's exact test and Chi-square test. Phylogenetic group B2 was the most prevalent although a great genetic diversity was observed by PFGE. Only genes associated to siderophores were found in ciprofloxacin-resistant isolates; however, in ciprofloxacin-susceptible isolates, genes related to siderophores and toxin, were detected. Additionally qnrB was detected in both populations, ciprofloxacin resistant and susceptible. DNA mutations in gyrA were Ser-83-Leu and Asp-87-Asn and in parC were Ser-80-Ile and Glu-84-Val, Glu-84-Lys. In conclusion, it was observed a high prevalence of qnrB in the population studied; in addition, it was the first time the pks island was observed only in ciprofloxacin-susceptible isolates.

Ståhl PL, Salmén F, Vickovic S, et al.
Visualization and analysis of gene expression in tissue sections by spatial transcriptomics.
Science. 2016; 353(6294):78-82 [PubMed] Related Publications
Analysis of the pattern of proteins or messengerRNAs (mRNAs) in histological tissue sections is a cornerstone in biomedical research and diagnostics. This typically involves the visualization of a few proteins or expressed genes at a time. We have devised a strategy, which we call "spatial transcriptomics," that allows visualization and quantitative analysis of the transcriptome with spatial resolution in individual tissue sections. By positioning histological sections on arrayed reverse transcription primers with unique positional barcodes, we demonstrate high-quality RNA-sequencing data with maintained two-dimensional positional information from the mouse brain and human breast cancer. Spatial transcriptomics provides quantitative gene expression data and visualization of the distribution of mRNAs within tissue sections and enables novel types of bioinformatics analyses, valuable in research and diagnostics.

Zhou B, Hu XM, Wu GY
Association between the XPG gene Asp1104His polymorphism and lung cancer risk.
Genet Mol Res. 2016; 15(2) [PubMed] Related Publications
It has been suggested that the xeroderma pigmentosum complementation group G (XPG) gene Asp1104His polymorphism is linked to susceptibility to lung cancer. However, the results from the published studies are contradictory rather than conclusive. With this meta-analysis, we aimed to achieve a better understanding of the effects of the XPG gene Asp1104His polymorphism on lung cancer risk. We identified six eligible studies from five publications that included a total of 2293 lung cancer patients and 2586 controls. There was a significant association between the XPG gene Asp1104His polymorphism and lung cancer (His/His vs Asp/Asp: OR = 1.24, 95%CI = 1.04-1.48; Asp/His vs Asp/Asp: OR = 1.17, 95%CI = 1.03-1.34; the dominant model: OR = 1.18, 95%CI = 1.04-1.33; the recessive model: OR = 1.10, 95%CI = 0.94-1.28). In a subgroup analysis by nationality, we found a significant association between the XPG gene Asp1104His polymorphism and lung cancer risk in Asians. No publication bias was found in this study. The results from this meta-analysis indicate that the XPG gene Asp1104His polymorphism is associated with lung cancer risk, especially in Asians.

Nicoś M, Krawczyk P, Powrózek T, et al.
PIK3CA Mutations Detected in Patients with Central Nervous System Metastases of Non-small Cell Lung Cancer.
Anticancer Res. 2016; 36(5):2243-9 [PubMed] Related Publications
BACKGROUND: In non-small cell lung cancer (NSCLC) the phosphatidylinositol-4,5-bisphosphate 3-kinase, catalytic subunit alpha (PIK3CA) gene mutations have been reported in fewer than 5% of primary tumors.
MATERIALS AND METHODS: We assessed PIK3CA gene mutations in 145 tissue samples from central nervous system (CNS) metastases of NSCLC using three polymerase chain reaction (PCR) techniques: high resolution melting-PCR (HRM-PCR), allele-specific-quantitative PCR (ASP-qPCR) and TaqMan PCR.
RESULTS: HRM analysis allowed us to select three PIK3CA-positive specimens (2.1% of the studied group) and ASP-qPCR techniques identified them as one E542K and two H1047R substitutions, which were confirmed by TaqMan probes. The PIK3CA mutations were indicated only in males (3% of all males). One of the patients was reported to be a non-smoker with adenocarcinoma (AC; 2.5% of the AC group), however, the other two patients were smokers with squamous cell carcinoma (SCC; 3.4% of SCC group).
CONCLUSION: This is the first report of the presence of PIK3CA gene mutation in CNS-metastatic lesions of NSCLC worldwide that could broaden therapeutic choices in such patients.

Chen W, Zhou P, Li X
High expression of DDX20 enhances the proliferation and metastatic potential of prostate cancer cells through the NF-κB pathway.
Int J Mol Med. 2016; 37(6):1551-7 [PubMed] Free Access to Full Article Related Publications
DEAD (Asp-Glu-Ala-Asp) box polypeptide 20 (DDX20), a member of the DEAD box protein family, encodes an RNA helicase. Previous research has revealed that DDX20 may act as a tumor suppressor in hepatocellular carcinoma and as a tumor promoter in breast cancer. These conflicting reports prompted us to explore the role of DDX20 in prostate cancer (PCa). To gain insight into the functions of DDX20 in PCa, we examined DDX20 expression patterns in a PCa tissue microarray with 99 PCa tissue samples. The results of immunohistochemical staining revealed that DDX20 expression is frequently upregulated in PCa tissues compared with that in the adjacent tissues and further clinicopathological analysis showed that the expression level of DDX20 closely correlates with tumor size, TNM stage (positive correlation) and patient prognosis (negative correlation). Both gain‑of- and loss‑of‑function assays were performed in vitro; the overexpression of DDX20 enhanced the proliferation and metastatic potential of cancer cells and this was examined by performing a cell counting kit-8 (CCK-8) assay, wound healing assay and Transwell migration assay. Furthermore, we found that there is a positive correlation between the expression of matrix metallopeptidase 9 (MMP9) and DDX20 expression. These findings led us to examine whether DDX20 may exert effects through the NF‑κB pathway. Luciferase reporter assays suggested that DDX20 altered the activity of NF-κB. Taken together, these findings show that DDX20 may promote the progression of PCa through the NF-κB pathway.

Cui L, Song Z, Liang B, et al.
Radiation induces autophagic cell death via the p53/DRAM signaling pathway in breast cancer cells.
Oncol Rep. 2016; 35(6):3639-47 [PubMed] Related Publications
Autophagy is known to play a role in the response of breast cancer cells to radiation therapy. However, the mechanisms that mediate the process of autophagy and contribute to radiation-induced cell death and cell survival remain to be fully characterized. Therefore, in this study, the functional role of autophagy in radiation-induced cytotoxicity in breast cancer cells was investigated. After MCF-7 cells were exposed to various doses of radiation, increased monodansylcadaverine (MDC) staining and a greater deposition of LC3-positive puncta were observed. Expression of the autophagy-related proteins, Beclin 1 and LC3-II, were also found to be upregulated. Radiation-induced autophagic cell death was partially abrogated following the administration of 3-methyladenine (3-MA) and in knockdown experiments of Atg5 and Beclin 1. In the gene microarray analysis performed after irradiation, a number of differentially expressed genes were identified. In particular, upregulation of both the mRNA and protein levels of the autophagy-related genes, DRAM and TIGAR, were detected. However, inhibition of autophagy by 3-MA reduced the radiation-induced upregulation of LC3-II and DRAM. Conversely, silencing of p53 downregulated the expression of LC3-II and DRAM following radiation. Silencing of DRAM reversed the upregulation of LC3-II and DRAM following radiation, partially blocked radiation-induced cell death, and no significant change in p53 expression was detected. Based on these results, the p53/DRAM signaling pathway appears to contribute to radiation-induced autophagic cell death in MCF-7 breast cancer cells.

Yang XJ, Si RH, Liang YH, et al.
Mir-30d increases intracellular survival of Helicobacter pylori through inhibition of autophagy pathway.
World J Gastroenterol. 2016; 22(15):3978-91 [PubMed] Free Access to Full Article Related Publications
AIM: To determine if mir-30d inhibits the autophagy response to Helicobacter pylori (H. pylori) invasion and increases H. pylori intracellular survival.
METHODS: The expression of mir-30d was detected by quantitative polymerase chain reaction (PCR), and autophagy level was examined by transmission electron microscopy, western blot, and GFP-LC3 puncta assay in human AGS cells and GES-1 cells. Luciferase reporter assay was applied to confirm the specificity of mir-30d regulation on the expression of several core molecules involved in autophagy pathway. The expression of multiple core proteins were analyzed at both the mRNA and protein level, and the intracellular survival of H. pylori after different treatments was detected by gentamicin protection assay.
RESULTS: Autophagy level was increased in AGS and GES-1 cells in response to H. pylori infection, which was accompanied by upregulation of mir-30d expression (P < 0.05, vs no H. pylori infection). In the two gastric epithelial cell lines, mimic mir-30d was found to repress the autophagy process, whereas mir-30d inhibitor increased autophagy response to H. pylori invasion. mir-30d mimic decreased the luciferase activity of wild type reporter plasmids carrying the 3' untranslated region (UTR) of all five tested genes (ATG2B, ATG5, ATG12, BECN1, and BNIP3L), whereas it had no effect on the mutant reporter plasmids. These five genes are core genes of autophagy pathway, and their expression was reduced significantly after mir-30d mimic transfection (P < 0.05, vs control cells without mir-30d mimic treatment). Mir-30d mimic transfection and direct inhibition of autophagy increased the intracellular survival of H. pylori in AGS cells.
CONCLUSION: Mir-30d increases intracellular survival of H. pylori in gastric epithelial cells through inhibition of multiple core proteins in the autophagy pathway.

Yao CA, Chen CC, Wang NP, Chien CT
Soy-Based Multiple Amino Acid Oral Supplementation Increases the Anti-Sarcoma Effect of Cyclophosphamide.
Nutrients. 2016; 8(4):192 [PubMed] Free Access to Full Article Related Publications
The use of a mixture of amino acids caused a selective apoptosis induction against a variety of tumor cell lines, reduced the adverse effects of anti-cancer drugs and increased the sensitivity of tumor cells to chemotherapeutic agents. We evaluated the effects and underlying mechanisms of soy-derived multiple amino acids' oral supplementation on the therapeutic efficacy of low-dose cyclophosphamide (CTX) and on tumor growth, apoptosis, and autophagy in severe combined immunodeficiency (SCID) mice that were injected with sarcoma-180 (S-180) cells. 3-methyladenine or siRNA knockdown of Atg5 was used to evaluate its effect on sarcoma growth. A comparison of mice with implanted sarcoma cells, CTX, and oral saline and mice with implanted sarcoma cells, CTX, and an oral soy-derived multiple amino acid supplement indicated that the soy-derived multiple amino acid supplement significantly decreased overall sarcoma growth, increased the Bax/Bcl-2 ratio, caspase 3 expression, and apoptosis, and depressed LC3 II-mediated autophagy. Treatment with 3-methyladenine or Atg5 siRNA elicited similar responses as CTX plus soy-derived multiple amino acid in downregulating autophagy and upregulating apoptosis. A low dose of CTX combined with an oral soy-derived multiple amino acid supplement had a potent anti-tumor effect mediated through downregulation of autophagy and upregulation of apoptosis.

Chen KH, Walker AM
Prolactin inhibits a major tumor-suppressive function of wild type BRCA1.
Cancer Lett. 2016; 375(2):293-302 [PubMed] Related Publications
Even though mutations in the tumor suppressor, BRCA1, markedly increase the risk of breast and ovarian cancer, most breast and ovarian cancers express wild type BRCA1. An important question is therefore how the tumor-suppressive function of normal BRCA1 is overcome during development of most cancers. Because prolactin promotes these and other cancers, we investigated the hypothesis that prolactin interferes with the ability of BRCA1 to inhibit the cell cycle. Examining six different cancer cell lines with wild type BRCA1, and making use of both prolactin and the growth-inhibiting selective prolactin receptor modulator, S179D PRL, we demonstrate that prolactin activation of Stat5 results in the formation of a complex between phospho-Stat5 and BRCA1. Formation of this complex does not interfere with nuclear translocation or binding of BRCA1 to the p21 promoter, but does interfere with the ability of BRCA1 to transactivate the p21 promoter. Overexpression of a dominant-negative Stat5 in prolactin-stimulated cells resulted in increased p21 expression. We conclude that prolactin inhibits a major tumor-suppressive function of BRCA1 by interfering with BRCA1's upregulation of expression of the cell cycle inhibitor, p21.

Gerges S, Rohde K, Fulda S
Cotreatment with Smac mimetics and demethylating agents induces both apoptotic and necroptotic cell death pathways in acute lymphoblastic leukemia cells.
Cancer Lett. 2016; 375(1):127-32 [PubMed] Related Publications
Treatment resistance in acute lymphoblastic leukemia (ALL) is often caused by defects in programmed cell death, e.g. by overexpression of Inhibitor of Apoptosis (IAP) proteins. Here, we report that small-molecule Smac mimetics (i.e. BV6, LCL161, birinapant) that neutralize x-linked IAP (XIAP), cellular IAP (cIAP)1 and cIAP2 cooperate with demethylating agents (i.e. 5-azacytidine (5AC) or 5-aza-2'-deoxycytidine (DAC)) to induce cell death in ALL cells. Molecular studies reveal that induction of cell death is preceded by BV6-mediated depletion of cIAP1 protein and involves tumor necrosis factor (TNF)α autocrine/paracrine signaling, since the TNFα-blocking antibody Enbrel significantly reduces BV6/5AC-induced cell death. While BV6/5AC cotreatment induces caspase-3 activation, the broad-range caspase inhibitor N-benzyloxycarbonyl-Val-Ala-Asp-fluoromethylketone (zVAD.fmk) only partly rescues ALL cells from BV6/5AC-induced cell death. This indicates that BV6/5AC cotreatment engages non-apoptotic cell death upon caspase inhibition. Indeed, genetic silencing of key components of necroptosis such as Receptor-Interacting Protein (RIP)3 or mixed lineage kinase domain-like (MLKL) in parallel with administration of zVAD.fmk provides a significantly better protection against BV6/5AC-induced cell death compared to the use of zVAD.fmk alone. Similarly, concomitant administration of pharmacological inhibitors of necroptosis (i.e. necrostatin-1s, GSK'872, dabrafenib, NSA) together with zVAD.fmk is superior in rescuing cells from BV6/5AC-induced cell death compared to the use of zVAD.fmk alone. These findings demonstrate that in ALL cells BV6/5AC-induced cell death is mediated via both apoptotic and necroptotic pathways. Importantly, BV6/5AC cotreatment triggers necroptosis in ALL cells that are resistant to apoptosis due to caspase inhibition. This opens new perspectives to overcome apoptosis resistance with important implications for the development of new treatment strategies for ALL.

Kimura K, Huang RC
Tetra-O-Methyl Nordihydroguaiaretic Acid Broadly Suppresses Cancer Metabolism and Synergistically Induces Strong Anticancer Activity in Combination with Etoposide, Rapamycin and UCN-01.
PLoS One. 2016; 11(2):e0148685 [PubMed] Free Access to Full Article Related Publications
The ability of Tetra-O-methyl nordihydroguaiaretic acid (M4N) to induce rapid cell death in combination with Etoposide, Rapamycin, or UCN-01 was examined in LNCaP cells, both in cell culture and animal experiments. Mice treated with M4N drug combinations with either Etoposide or Rapamycin showed no evidence of tumor and had a 100% survival rate 100 days after tumor implantation. By comparison all other vehicles or single drug treated mice failed to survive longer than 30 days after implantation. This synergistic improvement of anticancer effect was also confirmed in more than 20 cancer cell lines. In LNCaP cells, M4N was found to reduce cellular ATP content, and suppress NDUFS1 expression while inducing hyperpolarization of mitochondrial membrane potential. M4N-treated cells lacked autophagy with reduced expression of BNIP3 and ATG5. To understand the mechanisms of this anticancer activity of M4N, the effect of this drug on three cancer cell lines (LNCaP, AsPC-1, and L428 cells) was further examined via transcriptome and metabolomics analyses. Metabolomic results showed that there were reductions of 26 metabolites essential for energy generation and/or production of cellular components in common with these three cell lines following 8 hours of M4N treatment. Deep RNA sequencing analysis demonstrated that there were sixteen genes whose expressions were found to be modulated following 6 hours of M4N treatment similarly in these three cell lines. Six out of these 16 genes were functionally related to the 26 metabolites described above. One of these up-regulated genes encodes for CHAC1, a key enzyme affecting the stress pathways through its degradation of glutathione. In fact M4N was found to suppress glutathione content and induce reactive oxygen species production. The data overall indicate that M4N has profound specific negative impacts on a wide range of cancer metabolisms supporting the use of M4N combination for cancer treatments.

Jeong JK, Gurunathan S, Kang MH, et al.
Hypoxia-mediated autophagic flux inhibits silver nanoparticle-triggered apoptosis in human lung cancer cells.
Sci Rep. 2016; 6:21688 [PubMed] Free Access to Full Article Related Publications
Solid tumors are frequently associated with resistance to chemotherapy because the fraction of hypoxic tumor cells is substantial. To understand the underlying mechanism of hypoxia on silver nanoparticle (AgNPs)-induced apoptosis, the expression of hypoxia-inducible factor (HIF)-1α, a hallmark of hypoxia, was measured in the presence and absence of AgNPs. The results showed that HIF-1α expression was upregulated after AgNPs treatment under both hypoxic and normoxic conditions. Cell viability assays showed that AgNPs promoted cell death in cancer cells but not in non-cancer cells, as cancer cells are slightly more acidic than normal cells. However, reactive oxygen species generation induced by AgNPs in lung cancer cells caused high susceptibility to oxidative stress, whereas pre-exposure to hypoxia blocked AgNPs-induced oxidative stress. Notably, HIF-1α inhibited AgNPs-induced mitochondria-mediated apoptosis by regulating autophagic flux through the regulation of ATG5, LC3-II, and p62. Further, cell viability after treatment of cancer cells with AgNPs under hypoxic conditions was lower in HIF-1α siRNA-transfected cells than in control siRNA-transfected cells, indicating that HIF-1α knockdown enhances hypoxia induced decrease in cell viability. Our results suggest that hypoxia-mediated autophagy may be a mechanism for the resistance of AgNPs-induced apoptosis and that strategies targeting HIF-1α may be used for cancer therapy.

Nicoś M, Krawczyk P, Jarosz B, et al.
Sensitive methods for screening of the MEK1 gene mutations in patients with central nervous system metastases of non-small cell lung cancer.
Clin Transl Oncol. 2016; 18(10):1039-43 [PubMed] Free Access to Full Article Related Publications
BACKGROUND: The mitogen-activated protein kinases 1 and 2 (MEK1, MEK2) are fundamental partners in the RAS-RAF-MEK-ERK pathway that is involved in regulation of cell proliferation, differentiation and survival. Downregulation of the MEK cascades has been implicated in acquiring of the malignant phenotype in various cancers. Somatic mutations in MEK1 gene (substitutions K57N, Q56P, D67N) were described in <1 % of non-small cell lung cancer (NSCLC) and they were more commonly reported in adenocarcinoma patients with current or former smoking status.
MATERIALS AND METHODS: In the following study, we assessed the MEK1 gene mutations in 145 FFPE tissue samples from central nervous system (CNS) metastases of NSCLC using HRM-PCR and ASP-qPCR techniques. The studied group was heterogeneous in terms of histopathology and smoking status. The prevalence of the MEK1 gene mutation was correlated with the occurrence of mutations in KRAS, EGFR, DDR2, PIK3CA, NRAS, HER2, AKT1 and PTEN genes.
RESULTS: Using HRM and ASP-qPCR methods we identified one (0.7 %; 1/145) MEK1 substitution (Q56P) in CNS metastases of NSCLC. The mutation was identified in a single, 50-year-old, current smoking men with adenocarcinoma (1.25 %; 1/80 of all adenocarcinomas).
CONCLUSIONS: According to the current knowledge, the incidence of MEK1 gene mutation in CNS metastatic lesion of NSCLC is the first such report worldwide. The analysis of gene profile in cancer patients may extend the scope of molecularly targeted therapies used both in patients with primary and metastatic tumors of NSCLC.

Xu YZ, Li YH, Lu WJ, et al.
YL4073 is a potent autophagy-stimulating antitumor agent in an in vivo model of Lewis lung carcinoma.
Oncol Rep. 2016; 35(4):2081-8 [PubMed] Related Publications
Cancer cells activate autophagy in response to anticancer therapies. Autophagy induction is a promising therapeutic approach to treat cancer. In a previous study, YL4073 inhibited the growth of liver cancer and induced liver cancer cell apoptosis. Here, we demonstrated the anticancer activity and specific mechanisms of YL4073 in Lewis lung carcinoma LL/2 cells. Our results show that YL4073-induced autophagy was followed by apoptotic cell death. The anticancer and autophagy stimulating efficacy was confirmed by several factors, including the appearance of autophagic vacuoles, formation of acidic vesicular organelles, recruitment of microtubule-associated protein 1 light chain 3 II (LC3-II) to the autophagosomes, conversion and cleavage of LC3-I to LC3-II, upregulation of Beclin 1 expression, and formation of the Atg12-Atg5 conjugate in LL/2 cells after YL4073 treatment for 24 or 48 h. Furthermore, P53 activation and p-histone H3 phosphorylation occurred after cell exposure to YL4073 for 48 h, suggesting that cell apoptosis had occurred. Pharmacological inhibition of autophagy using 3-methyladenine increased cell apoptosis. Molecular level studies revealed that YL4073 inhibited survival signalling by blocking the activation of Akt and mTOR phosphorylation and reduced the expression of p-mTOR downstream targets for phosphorylation, including p70S6K, p-TSC, p-MAPK, and p-AMPK. This suggests that the Akt/mTOR/p70S6K and TSC/MAPK/AMPK pathways are involved in the effects of YL4073 treatment in LL/2 cells. In addition, YL4073 significantly inhibited LL/2 tumor growth and induced apoptosis in vivo. These data suggest that YL4073 has a significant anticancer effect, with a pathway-specific mechanism of autophagy both in vitro and in vivo.

Yin R, Guo L, Zhang J, et al.
RGD and polyhistidine tumor homing peptides potentiates the action of human Maspin as an antineoplastic candidate.
Appl Microbiol Biotechnol. 2016; 100(14):6209-18 [PubMed] Related Publications
Maspin, a non-inhibitory member of serine protease family, acts as an effective tumor suppressor by inhibiting cell inhesion and mobility. We found that exogenous wild-type rMaspin had a low effect on tumor growth in vivo. However, when the peptide Arg-Gly-Asp-hexahistidine (RGD-6His) was introduced into rMaspin, the modified rMaspin showed significant inhibitory activity in angiogenic assays and tumor-bearing animal models. Overall, our data suggested that both the RGD and hexahistidine fragments contributed to improve the fusion protein activity and polyhistidine peptide could be considered as flexible linker to separate RGD and Maspin moieties to avoid function interference. Besides, it is an efficient tag to achieve purified recombinant proteins. Furthermore, rMaspin fusing with RGD and hexahistidine could be a viable anticancer candidate.

Li P, Guo Y, Bledsoe G, et al.
Kallistatin induces breast cancer cell apoptosis and autophagy by modulating Wnt signaling and microRNA synthesis.
Exp Cell Res. 2016; 340(2):305-14 [PubMed] Free Access to Full Article Related Publications
Kallistatin is an endogenous protein that regulates differential signaling pathways and biological functions. Our previous studies showed that kallistatin gene therapy inhibited angiogenesis, tumor growth and metastasis in mice, and kallistatin protein suppressed Wnt-mediated growth, migration and invasion by blocking Wnt/β-catenin signaling pathway in breast cancer cells. In this study, we show that kallistatin reduced cell viability, and increased apoptotic cell death and caspase-3 activity in MDA-MB-231 breast cancer cells. Kallistatin also induced cancer cell autophagy, as evidenced by increased LC3B levels and elevated Atg5 and Beclin-1 expression; however, co-administration of Wnt or PPARγ antagonist GW9662 abolished these effects. Moreover, kallistatin via its heparin-binding site antagonized Wnt3a-induced cancer cell proliferation and increased PPARγ expression. Kallistatin inhibited oncogenic miR-21 synthesis associated with reduced Akt phosphorylation and Bcl-2 synthesis, but increased BAX expression. Kallistatin via PKC-ERK activation reduced miR-203 levels, leading to increased expression of suppressor of cytokine signaling 3 (SOCS3), a tumor suppressor. Conversely, kallistatin stimulated expression of the tumorigenic suppressors miR-34a and p53. Kallistatin's active site is essential for suppressing miR-21 and miR-203, and stimulating miR-34a and SOCS3 expression. This is the first study to demonstrate that kallistatin's heparin-binding site is essential for inhibiting Wnt-mediated effects, and its active site plays a key role in regulating miR-21, miR-203, miR-34a and SOCS3 synthesis in breast cancer cells. These findings reveal novel mechanisms of kallistatin in inducing apoptosis and autophagy in breast cancer cells, thus inhibiting tumor progression by regulation of Wnt/PPARγ signaling, as well as miR-21, miR-203 and miR-34a synthesis.

Yin G, Xiao Z, Ni Y, et al.
Association of MDR1 single-nucleotide polymorphisms and haplotype variants with multiple myeloma in Chinese Jiangsu Han population.
Tumour Biol. 2016; 37(7):9549-54 [PubMed] Related Publications
Multidrug resistance 1 (MDR1) gene encodes P-glycoprotein (P-gp), which acts as an efflux pump and provides cell protection against various substances, and its single-nucleotide polymorphisms (SNPs) are associated with the development of malignant hematologic diseases. The present study aimed at investigating whether the MDR1 SNPs and haplotype variants were correlated with the susceptibility to multiple myeloma (MM). A total of 115 MM patients and 153 healthy controls from Jiangsu Han population were enrolled and genotyped by polymerase chain reaction-allele-specific primer (PCR-ASP) method or DNA direct sequencing at MDR1 loci of C1236T, G2677T/A, and C3435T. No significance was found in the distribution of alleles and genotypes in MDR1 three loci. Diplotype analysis has also demonstrated no effect in susceptibility to MM. But, in haplotype analysis, the haplotype of T-G-T was significantly more common than healthy controls (12.6 % in MM group vs. 1.7 % in control group, odds ratios (ORs) = 8.7, 95 % confidence interval (CI) 3.3-22.8, Pc  < 0.01). Our results pointed out that comparable allele, genotype, and diplotype frequencies among MM patients and controls in Chinese Jiangsu Han population were found; the frequency of T-G-T haplotype was significantly increased in MM group compared with the control group, which indicated that this haplotype might be associated with the susceptibility to MM.

Fader CM, Salassa BN, Grosso RA, et al.
Hemin induces mitophagy in a leukemic erythroblast cell line.
Biol Cell. 2016; 108(4):77-95 [PubMed] Related Publications
BACKGROUND INFORMATION: In eukaryotic cells, autophagy is considered a lysosomal catabolic process which participates in the degradation of intracellular components in a vacuolar structure termed autolysosome. This pathway plays a significant role in the erythropoiesis process, contributing to the clearance of some organelles (such as mitochondria) that are not necessary in the mature red blood cells. Nevertheless, the role of autophagy in erythrocyte maturation has not been fully established.
RESULTS: Here, we have demonstrated that hemin (a physiological erythroid maturation stimulator) is able to induce the expression of critical autophagic genes (i.e., Map1a1b (LC3), Beclin-1 gen, Atg5) in an erythroleukemia cell type. We have also shown that hemin increased the size of autophagic vacuoles which were labelled with LC3 and the degradative lysosomal marker dye quenched-bovine serum albumin. In addition, we have determined by Western blot a rise in the lipidated form of the autophagic protein LC3 (i.e., LC3-II) upon hemin treatment. Moreover, we provide evidence that hemin induces mitochondrial membrane depolarisation and that mitochondria sequestration by autophagy requires the active form of the NIX protein.
CONCLUSIONS: We have found that the physiological erythroid maturation stimulator hemin is able to induce mitophagy in K562 cells, and that the autophagy adaptor NIX is necessary for mitophagy progression. K562 cells have been used as a relevant model to determine the possible therapeutic role of new differentiating compounds.
SIGNIFICANCE: It has been proposed that autophagy induction is a feasible new therapeutic key in fighting cancer. Our results suggest that hemin is favoring erythroid maturation by inducing an autophagic response in K562 cells, being a possible therapeutic candidate that may help in the chronic myelogenous leukemia (CML) treatment.

Stepien M, Fedirko V, Duarte-Salles T, et al.
Prospective association of liver function biomarkers with development of hepatobiliary cancers.
Cancer Epidemiol. 2016; 40:179-87 [PubMed] Related Publications
INTRODUCTION: Serum liver biomarkers (gamma-glutamyl transferase, GGT; alanine aminotransferase, ALT; aspartate aminotransferase, AST; alkaline phosphatase, ALP; total bilirubin) are used as indicators of liver disease, but there is currently little data on their prospective association with risk of hepatobiliary cancers.
METHODS: A nested-case control study was conducted within the prospective EPIC cohort (>520,000 participants, 10 European countries). After a mean 7.5 mean years of follow-up, 121 hepatocellular carcinoma (HCC), 34 intrahepatic bile duct (IHBC) and 131 gallbladder and biliary tract (GBTC) cases were identified and matched to 2 controls each. Circulating biomarkers were measured in serum taken at recruitment into the cohort, prior to cancer diagnosis. Multivariable adjusted conditional logistic regression was used to calculate odds ratios and 95% confidence intervals (OR; 95%CI).
RESULTS: In multivariable models, 1SD increase of each log-transformed biomarker was positively associated with HCC risk (OR(GGT)=4.23, 95%CI:2.72-6.59; OR(ALP)=3.43, 95%CI:2.31-5.10;OR(AST)=3.00, 95%CI:2.04-4.42; OR(ALT)=2.69, 95%CI:1.89-3.84; OR(Bilirubin)=2.25, 95%CI:1.58-3.20). Each liver enzyme (OR(GGT)=4.98; 95%CI:1.75-14.17; OR(AST)=3.10, 95%CI:1.04-9.30; OR(ALT)=2.86, 95%CI:1.26-6.48, OR(ALP)=2.31, 95%CI:1.10-4.86) but not bilirubin (OR(Bilirubin)=1.46,95%CI:0.85-2.51) showed a significant association with IHBC. Only ALP was significantly associated with GBTC risk (OR(ALP)=1.59, 95%CI:1.20-2.09).
CONCLUSION: This study shows positive associations between circulating liver biomarkers in sera collected prior to cancer diagnoses and the risks of developing HCC or IHBC, but not GBTC.

Antonietti P, Gessler F, Düssmann H, et al.
AT-101 simultaneously triggers apoptosis and a cytoprotective type of autophagy irrespective of expression levels and the subcellular localization of Bcl-xL and Bcl-2 in MCF7 cells.
Biochim Biophys Acta. 2016; 1863(4):499-509 [PubMed] Related Publications
The effects of autophagy on cell death are highly contextual and either beneficial or deleterious. One prime example for this dual function of autophagy is evidenced by the cell responses to the BH3 mimetic AT-101 that is known to induce either apoptotic or autophagy-dependent cell death in different settings. Based on previous reports, we hypothesized that the expression levels of pro-survival Bcl-2 family members may be key determinants for the respective death mode induced by AT-101. Here we investigated the role of autophagy in the response of MCF7 breast cancer cells to AT-101. AT-101 treatment induced a prominent conversion of LC3-I to LC3-II and apoptotic cell death characterized by the appearance of Annexin-positive/PI-negative early apoptotic cells and PARP cleavage. Inhibition of the autophagy pathway, either through application of 3-MA or by lentiviral knockdown of ATG5, strongly potentiated cell death, indicating a pro-survival function of autophagy. Overexpression of wild type Bcl-xL significantly diminished the net amount of AT-101-induced cell death, but failed to alter the death-enhancing effects of the ATG5 knockdown. This was also observed with the organelle-specific variants Bcl-xL-ActA and Bcl-2-ActA (mitochondrial) as well as Bcl-xL-cb5 and Bcl-2-cb5 (ER) which all reduced AT-101-induced cell death, but did not affect the death-enhancing effects of 3-MA. Collectively, our data indicate that in apoptosis-proficient MCF7 cells, AT-101 triggers Bcl-2- and Bcl-xL-dependent apoptosis and a cytoprotective autophagy response that is independent of the expression and subcellular localization of Bcl-xL and Bcl-2.

Liu FL, Mo EP, Yang L, et al.
Autophagy is involved in TGF-β1-induced protective mechanisms and formation of cancer-associated fibroblasts phenotype in tumor microenvironment.
Oncotarget. 2016; 7(4):4122-41 [PubMed] Free Access to Full Article Related Publications
Transforming growth factor-β1 (TGF-β1) present in tumor microenvironment acts in a coordinated fashion to either suppress or promote tumor development. However, the molecular mechanisms underlying the effects of TGF-β1 on tumor microenvironment are not well understood. Our clinical data showed a positive association between TGF-β1 expression and cancer-associated fibroblasts (CAFs) in tumor microenvironment of breast cancer patients. Thus we employed starved NIH3T3 fibroblasts in vitro and 4T1 cells mixed with NIH3T3 fibroblasts xenograft model in vivo to simulate nutritional deprivation of tumor microenvironment to explore the effects of TGF-β1. We demonstrated that TGF-β1 protected NIH3T3 fibroblasts from Star-induced growth inhibition, mitochondrial damage and cell apoptosis. Interestingly, TGF-β1 induced the formation of CAFs phenotype in starvation (Star)-treated NIH3T3 fibroblasts and xenografted Balb/c mice, which promoted breast cancer tumor growth. In both models, autophagy agonist rapamycin increased TGF-β1-induced protective effects and formation of CAFs phenotypes, while autophagy inhibitor 3-methyladenine, Atg5 knockdown or TGF-β type I receptor kinase inhibitor LY-2157299 blocked TGF-β1 induced these effects. Taken together, our results indicated that TGF-β/Smad autophagy was involved in TGF-β1-induced protective effects and formation of CAFs phenotype in tumor microenvironment, which may be used as therapy targets in breast cancer.

Sun YW, Chen KY, Kwon CH, Chen KM
CK0403, a 9‑aminoacridine, is a potent anti‑cancer agent in human breast cancer cells.
Mol Med Rep. 2016; 13(1):933-8 [PubMed] Related Publications
3‑({4‑[4‑(Acridin‑9‑ylamino)phenylthio]phenyl}(3‑hydroxypropyl)amino)propan‑1‑ol (CK0403) is a sulfur‑containing 9‑anilinoacridine analogue of amsacrine and was found to be more potent than its analogue 2-({4-[4-(acridin-9-ylamino)phenylthio]phenyl}(2‑hydroxyethyl)amino)ethan‑1‑ol (CK0402) and amsacrine in the inhibition of the topoisomerase II‑catalyzed decatenation reaction. A previous study by our group reported that CK0402 was effective against numerous breast cancer cell lines, and the combination of CK0402 with herceptin enhanced its activity in HER2(+) SKBR‑3 cells. In order to identify novel chemotherapeutic agents with enhanced potency, the present study explored the potential of CK0403 in the treatment of breast cancer. First, the growth inhibitory activity of CK0403 in the breast cancer cell lines MCF‑7, MDA‑MB‑231, BT474 and SKBR‑3, as well as in the non‑cancerous MCF‑10A cell line, was examined using a sulforhodamine B assay. The results showed that CK0403 exerted more potent growth inhibitory activity than CK0402 in all of the breast cancer cell lines except MCF‑7. SKBR‑3 and MDA‑MB‑231 were the most sensitive cell lines tested, and the combination of CK0403 with herceptin in HER2(+) SKBR‑3 cells enhanced the growth inhibitory activity of CK0403. Analysis of cell cycle alterations induced by CK0403 in SKBR‑3 cells revealed that, similarly to CK0402, CK0403 induced G2/M‑phase arrest with a decreased S- and G0/G1-phase ratio. In addition, it was shown that CK0403 induced apoptosis more effectively than CK0402 in SKBR‑3 cells. Further analysis of autophagy protein 5 (Atg5) indicated that CK0403 induced more cleaved Atg5 than CK0402 and other chemotherapeutic agents tested. Of note, although still relatively potent, CK0403 exhibited reduced growth inhibitory activity under hypoxic conditions, which can induce autophagy. Collectively, the present results supported that CK0403 is highly potent and more effective than CK0402 against estrogen receptor-negative and HER2‑overexpressing breast cancer cell lines, suggesting its future application for chemotherapy in breast cancer.

Obón-Santacana M, Lujan-Barroso L, Travis RC, et al.
Acrylamide and Glycidamide Hemoglobin Adducts and Epithelial Ovarian Cancer: A Nested Case-Control Study in Nonsmoking Postmenopausal Women from the EPIC Cohort.
Cancer Epidemiol Biomarkers Prev. 2016; 25(1):127-34 [PubMed] Related Publications
BACKGROUND: Acrylamide was classified as "probably carcinogenic to humans (group 2A)" by the International Agency for Research on Cancer. Epithelial ovarian cancer (EOC) is the fourth cause of cancer mortality in women. Five epidemiological studies have evaluated the association between EOC risk and dietary acrylamide intake assessed using food frequency questionnaires, and one nested case-control study evaluated hemoglobin adducts of acrylamide (HbAA) and its metabolite glycidamide (HbGA) and EOC risk; the results of these studies were inconsistent.
METHODS: A nested case-control study in nonsmoking postmenopausal women (334 cases, 417 controls) was conducted within the European Prospective Investigation into Cancer and Nutrition (EPIC) cohort. Unconditional logistic regression models were used to estimate ORs and 95% confidence intervals (CI) for the association between HbAA, HbGA, HbAA+HbGA, and HbGA/HbAA and EOC and invasive serous EOC risk.
RESULTS: No overall associations were observed between biomarkers of acrylamide exposure analyzed in quintiles and EOC risk; however, positive associations were observed between some middle quintiles of HbGA and HbAA+HbGA. Elevated but nonstatistically significant ORs for serous EOC were observed for HbGA and HbAA+HbGA (ORQ5vsQ1, 1.91; 95% CI, 0.96-3.81 and ORQ5vsQ1, 1.90; 95% CI, 0.94-3.83, respectively); however, no linear dose-response trends were observed.
CONCLUSION: This EPIC nested case-control study failed to observe a clear association between biomarkers of acrylamide exposure and the risk of EOC or invasive serous EOC.
IMPACT: It is unlikely that dietary acrylamide exposure increases ovarian cancer risk; however, additional studies with larger sample size should be performed to exclude any possible association with EOC risk.

Zhao J, Nie Y, Wang H, Lin Y
MiR-181a suppresses autophagy and sensitizes gastric cancer cells to cisplatin.
Gene. 2016; 576(2 Pt 2):828-33 [PubMed] Related Publications
A number of chemotherapy drugs can induce autophagy. This inducible autophagy is a pro-survival mechanism and contributes to the development of acquired drug resistance. Emerging evidence indicates that miRNA regulates autophagy via targeting autophagy related genes and is involved in drug resistance. We previously demonstrated that miR-181a plays an important role in gastric cancer. The present study aimed to explore the effect of miR-181a on autophagy regulation and cisplatin resistance. We revealed that miR-181a is a novel negative regulator of autophagy in cisplatin-resistant cells SGC7901/CDDP. Then we indicated that ATG5 was a potential target of miR-181a. Furthermore, overexpression of miR-181a significantly enhanced the sensitivity of SGC7901/CDDP cells to cisplatin in vitro and reduced the volumes of gastric tumor xenografts in nude mice. Our finding provides evidence that miR-181a functions as a primary autophagy-related modulator and reverses cisplatin-resistance in GC cells.

Pettersen K, Monsen VT, Hakvåg Pettersen CH, et al.
DHA-induced stress response in human colon cancer cells - Focus on oxidative stress and autophagy.
Free Radic Biol Med. 2016; 90:158-72 [PubMed] Related Publications
Polyunsaturated fatty acids (PUFAs) are important constituents of the diet and health benefits of omega-3/n-3 PUFAs, especially eicosapentaenoic acid (EPA, 20:5 n-3) and docosahexaenoic acid (DHA, 22:6 n-3) have been well documented in relation to several diseases. Increasing evidence suggests that n-3 PUFAs may have anticancer activity and improve the effect of conventional cancer therapy. The mechanisms behind these effects are still unclear and need to be elucidated. We have examined the DHA-induced stress response in two human colon cancer cell lines, SW620 and Caco-2. SW620 cells are growth-inhibited at early time points by DHA, while the growth of Caco-2 cells almost remains unaffected by the same treatment. Gene expression analysis of SW620 cells treated with DHA revealed changes at early time points; transcripts involved in oxidative stress and autophagy were among the first to be differentially expressed. We find that oxidative stress is induced in both cell lines, although at different time points and to different extent. DHA induced nuclear translocation of the oxidative stress sensor NFE2L2 in both cell lines, indicating an induction of an anti-oxidative response. However, vitamin E did not counteract ROS-production or the translocation of NFE2L2 to the nucleus. Neither vitamin E nor the antioxidants butylated hydoxyanisole (BHA) and butylated hydoxytoluene (BHT) did affect the growth inhibition in SW620 cells after DHA-treatment. Also, siRNA-mediated down-regulation of NFE2L2 did not sensitize SW620 and Caco-2 cells to DHA. These results indicate that oxidative stress response is not the cause of DHA-induced cytotoxicity in SW620 cells. Using biochemical and imaging based functional assays, we found a low basal level of autophagy and no increase in autophagic flux after adding DHA to the SW620 cells. However, Caco-2 cells displayed a higher level of autophagy, both in the absence and presence of DHA. Inhibition of autophagy by siRNA mediated knock down of ATG5 and ATG7 sensitized both SW620 and Caco-2 cells to DHA. Stimulation of autophagy by rapamycin in SW620 and Caco-2 cells resulted in decreased DHA-sensitivity and inhibition of autophagy in Caco-2 cells by chloroquine resulted in increased DHA-sensitivity. These results suggest that autophagy is important for the DHA sensitivity of colon cancer cells and imply possible therapeutic effects of this fatty acid against cancer cells with low autophagy.

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